After discussion of a case an outline is given of the historical development of the concept of paranoia. Kraepelin gave a narrow definition of paranoia, which made strict differentiation of dementia praecox possible. Later researchers doubted if paranoia has a separate entity. Based on recent research paranoia, now called delusional disorder, was incorporated in DSM-III and DSM-III-R. Though the criteria were made less strict, this means a return to Kraepelin s views.

Views on the etiology of paranoia move between the poles that were given by Kraepelin, who stressed constitutional factors, and on the other hand Freud, who gave a psychodynamic explanation. Later clinicians followed at first Kraepelin, but more and more the importance of interactions with the environment, especially in the early phases of life, has been recognised. This leads to better understanding of the content of the delusion, but the question remains how much this adds to the explanation of the _ psychotic _ form.